1. Field of the Invention
The present invention relates to a car navigation system, and more particularly, to an apparatus and method for guiding a vehicle which is capable of accurately detecting a position of a vehicle moving on a road regardless of a location or an environment of the road, so that the current position of the vehicle, its advancing direction and a remaining distance to its destination can be informed to a driver through a voice guidance and a graphic display, thereby guiding the vehicle accurately and steadily to an intended destination.
2. Description of the Background Art
In general, a car navigation system is characterized in that positions of roads and facilities on a map are digitized and stored in a memory, and history of current position information on a vehicle is periodically analyzed by using satellites and maps with the roads of the map stored in the memory, thereby guiding the vehicle steadily to the destination within the shortest time.
In most car navigation systems, there is expressed only a simple operation for shortest path selection from an arbitrary starting position to a destination, which does not give the driver any current traffic condition
Recently, there has been proposed a method of guiding a car navigation system in which traffic information is received by a data file to thereby search a shortest path for guidance. This method employs a global positioning system (GPS).
The GPS system in use for the traffic information collection system is a space-based satellite radio navigation system developed by the U.S. Department of Defense which includes an intentional error in transmission in order to prevent a military use by other countries.
According to this system, by receiving radio signal transmitted from at least three or four satellites among many GPS satellites having an atomic frequency in the orbit, a distance to the satellites is obtained from the radio time of the radio signals, for which a speed measurement is available by using the Doppler effect of a three-dimensional or two-dimensional lateral position and the radio waves.
As aforementioned, the global positioning system (GPS) was initially developed for military use, as it was confirmed to have a high utility value for civil vehicle means, the satellite started a service for civil use, by transmitting radio signals for measurement which contains the range error.
By applying the global positioning system to the car navigation system, information on a vehicle operation, such as a distance to the destination and the time required, can be obtained.
Typically, the error in the distance signal received from the GPS satellite is approximately in the range of 100 m to 2 km.
FIGS. 1 and 2 show an apparatus for guiding a vehicle using the conventional global positioning system.
The apparatus for guiding a vehicle of the conventional art includes a plurality of GPS satellites 20 placed in a orbit for transmitting a GPS signal including position information and time information on a vehicle; and a GPS receiver 10 mounted in the vehicle for receiving the GPS signals including the position and time information from the plurality of GPS satellites 20, detecting a current position of the moving vehicle by using the GPS signals, and guiding the vehicle to its destination.
As shown in FIG. 2, the GPS receiver 10 includes an antenna 100 for receiving the GPS signal including the position and time information of the vehicle from the plurality of satellites 20; a frequency down converter 101 for frequency down converting the plurality of GPS signals each in the different range of a few GHz(substantially 1-8 GHz) as received to baseband signals; a GPS tuner 102 for extracting only a GPS signal corresponding to the current position of the vehicle from the frequency down converted baseband signals; a position operation unit 103 for computing an absolute coordinate of a latitude, a longitude, an altitude, and a standard time with the extracted GPS signal and outputting current position information on the vehicle; a compact disk player 106 having a disk ROM storing digitized positions of roads and facilities of a map; an operating panel 107 for inputting a position of a starting position or a destination; a CPU 105 for analyzing history of position information transmitted periodically from the position operation unit 103 to correct a position measurement error, and mapping the current position of the vehicle to each road on the map as stored in the disk ROM of the compact disk player 106; and a monitor 104 for displaying drive guide information outputted from the CPU 105 on a screen until it reaches a destination designated by the operating panel 107.
FIG. 3 is a flow chart of the process of the method for guiding a vehicle in which the GPS signal transmitted from the GPS satellites 20 is received, by which the current position of the vehicle is computed, and the computed current position of the vehicle is mapped onto the road of the map stored in the disk ROM of the compact disk player 106, thereby guiding the vehicle to its destination through the shortest path.
The operation of the apparatus for guiding a vehicle using the global positioning system in accordance with the conventional art will now be described with reference to FIG. 3.
When the car navigation system adapting the global positioning system is started to be operated, the CPU 105 actuates the compact disk player 106. Accordingly, the compact disk player 106 loads the map stored in the disk ROM as digitized and displays it on the screen of the monitor 104 through the CPU 105.
When positions of the roads and the facilities of the map is displayed on the screen of the monitor 104, a driver inputs a desired destination through the operating panel 107 (step S10).
At this time, the plurality of GPS satellites 20 placed in the orbit, that is, the 24 GPS satellites, transmits the GPS radio waves including the position and time information of the vehicle.
The GPS radio waves transmitted from the plurality of satellites 20 are received by the GPS receiver 10 mounted in the vehicle as shown in FIG. 1.
As shown in FIGS. 1 and 2, the GPS receiver 10 mounted in the vehicle receives the radio waves from at least three or four GPS satellites 20 (preferably three GPS satellites) among the plurality of GPS satellites 20 through a radio wave receiver such as the antenna 100, and supplies them to the frequency down converter 101.
The frequency down converter 101 frequency down converts the received GPS radio waves of a few GHz to baseband signals and supplies the same to the GPS tuner 102.
The GPS tuner 102 extracts only a corresponding baseband signal that is the most suitable to its position among the baseband signals for each GPS signal inputted through the frequency down converter 101.
The position operation unit 103 computes the current position of a vehicle, that is, a latitude, a longitude, an altitude and the standard time, on the basis of respective baseband signals inputted through the GPS tuner 102, and provides it to the CPU 105 (to be described later).
As is known, the GPS signal is a signal transmitted from the plurality of GPS satellites 20 having time information. Arrival time taken for the radio waves to reach the vehicle from the respective GPS satellite 20 is different to each other due to the difference of the distance from each GPS satellite to the vehicle.
By comparing the GPS signal arrival time from each GPS satellite pre-set over a reference coordinate corresponding to a specific position and a GPS signal arrival time from each GPS satellite received at a position of a specific position, an absolute coordinate value of the current specific vehicle can be obtained.
Accordingly, the CPU 105 reads out the current position information on the vehicle which was arithmetically operated by the position operation unit 103 and map-matches it with the road on the map as stored in the disk ROM of the compact disk player 106, so that the driver can recognize the current vehicle position and inputs a starting position through the operating panel (stage: ST11).
Accordingly, as the starting position is set, the CPU 105 receives various traffic data continuously and periodically as transmitted and displays them on the screen of the monitor 104 (stage: ST12).
In this respect, the CPU 105 searches the shortest path on the basis of the traffic data (stage: ST13) and displays it on the screen of the monitor 104.
When the vehicle starts moving along the path from the starting position (stage: ST15), the CPU 105 corrects an error of the position information periodically inputted from the position operation unit 103 and computes an average speed on the basis of an average time according to the moving distance for a predetermined time.
And, the CPU 105 analyzes the history of the position information, and periodically performs an arithmetic operation and numerical operation for map-matching the current position of the vehicle with the route of the map, and then displays it on the screen of the monitor 104.
Also, the CPU 103 continuously searches the data inputted from the numerical operating unit 103 so as to judge whether any abnormal situation occurs during driving (stage: ST16).
In case that an abnormal situation occurs, the CPU 103 searches again the shortest path on the basis of the received data and provides the driver with new information (stage: ST17).
Such processing is continuously performed according to a predetermined order until the driver reaches a destination set through the operating panel 107 (stage: ST18).
According to the method for guiding a vehicle using the global positioning system of the conventional art, the current position of the vehicle is computed by receiving the radio waves from at least three satellites among the plurality of GPS satellite placed in the orbit, and the history of the computed position information is analyzed so as to be map-matched with the route of the map as stored, thereby guiding to the destination.
However, the method for guiding a vehicle using the global positioning system of the conventional art has the following problems when the current position of the vehicle is detected and guided for traveling.
First, since the error is intentionally included for transmission from the GPS satellite, in case that the position is sensed by using the GPS receiver, the position error is wide-ranged from 100 m to 2 km, making it difficult to detect an accurate position of the vehicle.
Secondly, a complicate logical operation and numerical computation should be performed for additionally correcting the position error.
Thirdly, regarding the fact that the current position of the vehicle is computed by receiving the radio waves from at least three or four satellites among the plurality of GPS satellites placed in the orbit, since less than four satellite can be available for simultaneously receiving by the vehicle in such an area where there is a tunnel, or in a mountainous area, or in the downtown area where there are many tall buildings, the accurate position of the vehicle is hardly detected.
Lastly, the GPS receiver including an attachment such as the disk ROM player must be installed in the vehicle: however, it is very costly, and as the vehicles installing it are increased in number, a considerable expense is inevitably consumed, resulting in an unwanted situation against the low-cost transportation policy.
In addition, use of a differential GPS may be considered as one method for avoiding such a measurement error which occurs when the absolute coordinate of the vehicle is computed by using the GPS radio waves, which, however, also requires additional apparatus and increases in the expense.
Therefore, an object of the present invention is to provide an apparatus and method for guiding a vehicle which is capable of steadily guiding a vehicle by accurately identifying a position of a vehicle on a road regardless of a location or an environment of the road, without any complicate logical operation and numerical computation for correcting a position error, and without an increase in the expense due to any additional attachment such as a disk ROM player.
Another object of the present invention is to provide an apparatus and method for guiding a vehicle which is capable of continuously tracing the current position of a moving vehicle without a position error even in a bad condition where GPS satellite radio waves are hardly received.
Still another object of the present invention is to provide an apparatus and method for guiding a vehicle which includes a position transmitter installed on road and a position receiver mounted in a vehicle so as to accurately detect the current position of a vehicle by using a wireless communication network without using GPS satellite radio waves.
Yet another object of the present invention is to provide an apparatus and method for guiding a vehicle which is capable of informing a user of the current position of a vehicle, an advancing direction, a remaining distance to destination or warning the user of any dangerous matters on or near a road by voice guidance or graphic display, so that a user can safely drive to the destination.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided a method for guiding a vehicle including: an installing a position transmitting device at key points of roadside, receiving position information and danger information on the road through a traffic information network, coding the same, and modulating and continuously transmitting the coded information to a vehicle; an information collecting step of receiving signal of a corresponding position of the vehicle moving on the road, continuously classifying and searching the information and the intensity of the signal as received; a position detecting step either by directly using the searched result without computation or by computing a travel distance of the vehicle; and a guide step of informing of the current position, an advancing direction of the vehicle and a remaining distance to its destination or danger information for guidance.
In order to attain the above object, there is also provided an apparatus for guiding a vehicle including a position transmitting device installed at key points on a road to transfer service information and a position receiving device mounted in a moving vehicle to receive the service information so as to guide the vehicle, wherein the position transmitting device includes: an interface unit for receiving traffic information for service to a vehicle moving on a road from a traffic information network; a memory for storing position information on the road and the traffic information received from the interface unit as code valued; a first communication module for modulating the position information and the traffic information as coded and stored in the memory and transmitting the same to each vehicle moving in the vicinity of the road through an antenna; and a first microprocessor for coding the position information on the road and the traffic information obtained by the interface unit, providing it to the memory, and controlling the transmitting operation of the first communication module and the receiving operation of the traffic information according to a due order, and the position receiving device includes: a second communication module for receiving the signal as modulated by the position transmitting device through the antenna, classifying the information and intensity of the signal from the received signal, and outputting the same; an analog-to-digital converter for digitizing the intensity of the signal as classified by the second communication module; a travel distance detector for measuring a travel distance of the vehicle and generating a pulse in proportion to the measured travel distance; a second microprocessor for detecting the current position of the vehicle on the basis of the information as classified by the second communication module, the digital value according to the intensity of the signal and the measured pulse, analyzing the data to output a corresponding position information, travel information and danger information, and periodically controlling the operation of the second communication module; and an information output unit for visually and acoustically guiding the position information, the travel information and the danger information as obtained by the second microprocessor.